Volume s1-19,
Issue 6,
1939

In the present clinical investigation only cases of intestinal amebiasis in which there was neither a present nor a past history of dysentery were studied. The cases comprised both symptom-less carriers of E. histolytica and infected individuals with complaints of varying severity. Control observations were made whenever feasible. Only those symptoms and signs were ascribed to E. histolytica after other possible causes had been ruled out. In all, 216 cases of non-dysenteric amebiasis were studied, of which 100 were found to have symptoms.

1.
A study of the occurrence of symptomatology in a selected group of 106 apparently healthy men harboring E. histolytica showed 46 or 43.4 per cent to have symptoms. A control group of 108 cases negative for intestinal protozoa revealed but 8 or 7.4 per cent to have complaints. Of the 106 cases of amebiasis only 13.2 per cent of the complaints were of any appreciable severity.

2.
Of 236 individuals harboring various intestinal protozoal species, but not E. histolytica, the percentage with symptoms was similar to that found in the non-parasitized group, with the exception of Dientamoeba fragilis in which 27.3 per cent of 44 cases presented symptoms. Similarly, some of the flagellates presented higher percentages than the control. An explanation of this apparent pathogenicity was offered.

3.
A study of the blood findings in 61 cases of apparently healthy carriers of E. histolytica showed no significant differences from the results obtained in a control group of an equal number of individuals not harboring the parasite.

4.
Despite the apparent trivial nature of the complaints presented by most of the cases in an ambulatory group, it was found by a study of various hospitalized groups that a considerable number of non-dysenteric amebic infections are severe enough to require hospitalization. In 47 such cases the disease picture was so obscure that only the finding of the parasite in the stool led to the proper diagnosis, and in these, specific anti-amebic treatment gave good results where other methods had failed.

5.
A study of the nature of complaints revealed these to be primarily referable to the gastro-intestinal tract, yet without blood and mucus in the stools and usually without bowel abnormalities which might suggest an amebic process. Complaints referable to both upper and lower gastro-intestinal tracts appeared with equal frequency. Complaints referable to other systems were seldom encountered. Chronicity, recurrency and mildness of the symptoms were characteristic features.

6.
A symptom-complex simulating subacute or chronic appendicitis was the most commonly observed syndrome in this series of non-dysenteric cases of amebiasis.

During the last three decades many surveys have been made on human intestinal parasites throughout the world. These surveys have included such population groups as armies, hospitals, inmates of jails, schools, orphan's homes, and asylums. The results of these surveys have shown that some human protozoa and helminth infections are not only tropical and subtropical in distributions, but may be quite common in the temperate zone.

Craig (1934) emphatically stressed the importance of the “amebiasis problem” in the United States. He also mentioned that about 5 to 10 per cent of the people of the United States are carriers of Endamoeba histolytica, and that every carrier, as soon as detected, should be treated and the infection eliminated. Craig (1939) tabulated the results of many surveys in the United States, and found that among 71,278 individuals examined the percentage infection was 10.5. This percentage approximates his estimate of the incidence of E. histolytica infection throughout the United States.

The problem of periodicity in the asexual cycle of Plasmodium nucleophilum has been carefully studied in five birds, together with certain other questions, such as the age of the red cell most commonly attacked by the parasite, and the possibility of exoerythrocytic stages in the vertebrate host. The results may be summarized as follows:

1.
Periodicity is marked in this species, and the length of the asexual cycle approximates twenty-four hours. There is however much variation in individual birds, and synchronicity is frequently slight. In general, the peak of segmentation occurs between 10 a.m. and 5 p.m.

2.
Mature gametocytes may be found at any time during the twenty-four hours. Peaks in gametocyte number tend to follow by a few hours peaks in schizont number, indicating that the time for maturation of the sexual stages is somewhat greater and their length of life longer. It was found that size of the gametocyte, when mature, was somewhat larger than that given in the original description. A further difference, which applies to the asexual as well as the sexual forms, is in the color of the pigment, which is yellowish-brown, particularly when the granules are small.

3.
The mean number of merozoites per schizont was found to be 6.09 ± 0.29, with a range of from three to ten.

4.
The proportion of schizonts is usually low in this species, even when segmentation is most active, and frequently does not exceed 10 per cent. This is especially true in the later stages of the infection, which suggests that the mortality of the developing parasites is always high, and especially so after the host has had time to set up an effective resistance.

5.
The proportion of young parasites in the younger erythrocytes was determined in one bird, from a series of smears made at different times during the twenty-four hours, and found to be high, but nevertheless considerably lower than that found in the other species of avian plasmodia so far critically examined—cathemerium, praecox (relictum), elongatum and circumflexum.

6.
Exoerythrocytic stages were searched for in six birds, but without success.

1.
Repeated mouse transfer did not enhance the virulence for mice of two strains of Blastomyces dermatitidis which had caused human blastomycosis. Virulence was judged by the duration of survival of the animals following intraperitoneal inoculation and the extent of the lesions produced.

2.
The yeast form of the two strains was obtained from the mycelial form as readily by growing the organism directly on blood agar at 37°C. as by first passing it through a mouse. The cultural and microscopic appearances of each organism on blood agar at 37°C. were not altered by repeated mouse transfer.

3.
The experimental results suggest that the virulence of this fungus, at least for mice, is an attribute which is not readily changed.

One of the chief difficulties in the preparation of yellow fever vaccine (Theiler and Smith (1), Smith, Penna and Paoliello (2)) is the filtration of the chick embryo suspension through the Seitz, E. K., disc. This filter retains variable amounts of the virus and even becomes entirely blocked if an attempt is made to use a suspension containing more than 15 per cent of chick embryo tissue. The elimination of filtration from the method of vaccine preparation would avoid a serious loss of virus and at the same time permit the use of whatever suspension of chick embryo may prove most satisfactory.

Repeated tests show that the chick embryo is rarely contaminated while in the egg. On the other hand, cultural methods indicate that a high percentage of egg shells contain living bacteria even after they have been painted with tincture of iodine and washed with alcohol.

The race of A. quadrimaculatus in our insectary colony of this species has now been maintained for at least seven years. We have no means of knowing the actual number of generations that have been passed in this artificial environment, but, assuming, what we regard as the conservative estimate of on the average one generation per month, the present tenants of the insectary are at least 84 generations removed from their wild progenitors. During this period there has been no introduction, from any source, of new stock.

It appeared desirable to ascertain whether in this interval there had been any change in the susceptibility of the insectary race to the McCoy strain of P. vivax, which has been propagated in our service during the same period. For purposes of the comparison there were employed wild female A. quadrimaculatus caught in diurnal resting places at the head of the Wacissa river (Jefferson County, Florida) about one-half mile from the site where the progenitors of the colony were secured.

Blood was taken from canaries with heavy infections of Plasmodium circumflexum and inoculated into seven splenectomized and four normal chicks. Low grade and short-lived infections were obtained in four of the splenectomized and one of the control chicks.

Attempts to transmit the infection from five of the splenectomized chicks to five other splenectomized chicks were unsuccessful.

Attempts to transmit the infection from the splenectomized chicks to canaries were successful in one case from a splenectomized chick which showed parasites, but were unsuccessful from a chick which showed no parasites and from another chick in which parasites were observed.

The results of these attempts to infect splenectomized chicks with P. circumflexum parallel those obtained by Manwell (1933) with normal chicks. In these experiments, the removal of the spleen apparently had no influence on the infection due probably to the fact that the fowl exhibits a great natural resistance to infection with this parasite. Whatever the mechanism of resistance may be, removal of the spleen did not noticeably reduce it.

The simplest and easiest method for the standardization of Leishmania tropica vaccine is with the Opacity Tubes of Brown.

Leishmania tropica is cultured on our leishmania medium (Senekji, 1939) for ten days. The growth from the surface of the solid medium is emulsified in saline solution. The suspension is quite granular, but by shaking the tube, the clumps break up, and a uniform suspension is obtained. All the leishmania should be in the motile flagellated leptomonad stage, because the post-flagellated forms are smaller and may lack the flagellum.

The suspension of Leishmania tropica culture is then diluted in saline solution to match the different standard opacity tubes which are manufactured by Messers Burroughs, Wellcome and Company, for the standardization of bacterial vaccines.

Counts are made of the standardized leptomonad suspension in the blood counting chamber, and the result is expressed in 1 cc.

This book of standard equipment for every bacteriological worker has in the first edition in five years received major revision, has been entirely rewritten and enlarged to more than 1000 pages, double the size of the first edition. The index has been greatly improved and is now excellent.

There has been extensive rearrangement of genera and nine generic terms added. The difficulty of satisfactorily classifying material supported by incomplete data has been partially met by placement of the indeterminate species in an appendix to each genus of the classified species. We wonder if Leptospira icteroides, here given the dignity of a classified species, should not have been dropped to the indeterminate group.

Consideration has been given to the decisions on nomenclature by the International Congresses of Microbiology and of the type species concept of the International Rules of Botanical Nomenclature of the Fifth International Botanical Congress.

This book is a very complete revision of the author's “Medical and Veterinary Entomology”, the second edition of which was published in 1923. Since that time much has been added to our knowledge of the subject and the present work is intended to bring to the student and physician, as well as workers in public health, the most important and recent data regarding the relation of arthropods to public health and the well-being of man and animals. To this end, the public health aspects of the subject have been stressed and the relation of arthropods to the transmission of disease has been emphasized.

The reviewer has read this book with much interest and is impressed with its value, especially to the public health worker and student. He has found that it is up-to-date as regards its contents and accurate in its statements regarding the relationship of arthropods to disease, while the advice it contains as to the destruction and the prevention of the breeding of the various arthropods of importance in human and animal disease is practical and should prove most useful.

This is a curious work treating of syphilis largely from the sociological stand-point, and contains much that is valuable but more that is merely interesting, but marred by the prejudices of the author who accepts certain theories and opinions upon insufficient evidence and from them draws conclusions which are at variance with the truth. For instance, his statement that syphilis is always incurable will not be accepted by most students of this infection, while he certainly goes too far in his condemnation of society and the medical profession regarding the handling of the sociological problems connected with the disease. In this country, at least, his reproaches regarding the ignorance in which the public is kept by the medical profession in respect to syphilis, are not deserved, for perhaps too much publicity is being given the subject leading to greatly exaggerated conceptions of its prevalence and importance.

An excellent text-book upon microbiology written especially for the medical student, and, as the author states in the Preface, one “that is concerned primarily with the fundamentals of the subject.”

The opening chapters upon the history of microbiology are good and well illustrated with portraits of the most eminent investigators, as Pasteur, Koch, Theobald Smith and others. These chapters furnish the student with information regarding the development of the various subjects embraced in the book, as bacteriology, protozoology, the filtrable viruses, etc., which is not usually presented in such texts and which should stimulate the student's interest. The author states that he has endeavored to present microbiology in a clear and relatively concise manner and the reviewer believes that he has done so and that the result is a very useful volume for the medical student and other students interested in the subject.

There are few typographical errors and the data presented are generally accurate and well up-to-date.